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118 lines
4.0 KiB
118 lines
4.0 KiB
from collections import defaultdict
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from string import ascii_uppercase
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from grid import Grid
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def main():
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with open("day20.txt") as input_file:
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lines = [l.rstrip() for l in input_file.readlines()]
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# Part 1
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maze = Maze(lines)
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maze.find_portals()
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min_steps = maze.count_min_steps(maze.entry, maze.exit)
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print("Min steps:", min_steps)
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# Part 2
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maze = Maze(lines, recurse=True)
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maze.find_portals()
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min_steps = maze.count_min_steps(maze.entry, maze.exit)
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print("Min steps in recursion:", min_steps)
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class Maze(Grid):
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TILE_PATH = "."
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TILE_WALL = "#"
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ENTRY_DG = "AA"
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EXIT_DG = "ZZ"
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def __init__(self, lines, recurse=False):
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super().__init__(value_factory=str, lines=lines)
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self.entry = None
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self.exit = None
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self.portals = {}
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self.recurse = recurse
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self.portal_is_outer = {}
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self.height = len(lines)
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self.width = max(len(line) for line in lines)
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def find_portals(self):
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portals = defaultdict(list)
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for x, y, v in list(self.values_gen()):
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if v in ascii_uppercase:
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rv = self.getv(x + 1, y)
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if rv and rv in ascii_uppercase:
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rrv = self.getv(x + 2, y)
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portal_pos = (x + 2, y) if rrv == Maze.TILE_PATH else (x - 1, y)
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portals[v + rv].append(portal_pos)
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self.portal_is_outer[portal_pos] = x == 0 or x == self.width - 2
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continue
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dv = self.getv(x, y + 1)
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if dv and dv in ascii_uppercase:
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ddv = self.getv(x, y + 2)
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portal_pos = (x, y + 2) if ddv == Maze.TILE_PATH else (x, y - 1)
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portals[v + dv].append(portal_pos)
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self.portal_is_outer[portal_pos] = y == 0 or y == self.height - 2
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self.entry = portals["AA"][0]
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self.exit = portals["ZZ"][0]
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for p in portals.values():
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if len(p) == 2:
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self.portals[p[0]] = p[1]
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self.portals[p[1]] = p[0]
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def dumb_print(self, rpos=None, level=0):
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for y, row in self.g.items():
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for x, v in row.items():
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pos = (x, y)
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if pos == rpos:
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v = "@"
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elif pos in (self.entry, self.exit):
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v = "▒" if not self.recurse or level == 0 else "#"
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elif pos in self.portals:
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v = "▒" if not self.recurse or level > 0 or not self.portal_is_outer[pos] else "#"
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print(v, end="")
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print()
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def bfs(self, start, end):
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discovered = defaultdict(lambda: Grid(value_factory=bool))
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discovered[0].setv(start[0], end[1], True)
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parents = {}
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q = [(start, 0)]
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while q:
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pos, level = q.pop(0)
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if pos == end and (not self.recurse or level == 0):
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return parents
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nears = self.near_objects(pos)
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is_portal = pos in self.portals
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if is_portal:
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nears[self.portals[pos]] = Maze.TILE_PATH
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for near_pos, near_tile in nears.items():
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if near_tile != Maze.TILE_PATH:
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continue
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near_level = level
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if self.recurse and is_portal and near_pos == self.portals[pos]:
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near_level += -1 if self.portal_is_outer[pos] else 1
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if near_level < 0 or discovered[near_level].getv(near_pos[0], near_pos[1]):
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continue
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discovered[near_level].setv(near_pos[0], near_pos[1], True)
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parents[(near_pos, near_level)] = (pos, level)
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q.append((near_pos, near_level))
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return None
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def count_min_steps(self, start, end):
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parents = self.bfs(start, end)
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count = 0
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pos = (end, 0)
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while pos != (start, 0):
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count += 1
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parent = parents[pos]
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pos = parent
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return count
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if __name__ == "__main__":
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main()
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